Light emitting device

Abstract

To provide a light emitting device capable of both high heat dissipation and suppression of warpage.SOLUTION: A light emitting device comprises a first substrate, a second substrate disposed on the first substrate, which is long in a first direction in top view and has a thermal expansion coefficient different from that of the first substrate, a plurality of light emitting elements arranged on a second substrate, and a bonding member that bonds the second substrate to the first substrate. The bonding member has a first portion whose length in the first direction is less than or equal to the length in a second direction perpendicular to the first direction, and a second portion disposed on both sides of the first portion in the first direction, with a Young's modulus lower than that of the first portion and a thermal conductivity lower than that of the first portion.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a light emitting device. [Background technology]

[0002] Light-emitting devices have been developed in which a circuit board is placed on a mounting board, and many light-emitting elements are placed on the circuit board. When many light-emitting elements are made to emit light at high brightness, a large amount of heat is generated, so the light-emitting device is required to have high heat dissipation properties. On the other hand, since the mounting board and the circuit board generally have different thermal expansion coefficients, the light-emitting device may warp due to the heating process during the manufacture of the light-emitting device. When warping occurs, the optical accuracy of the light-emitting device decreases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-027116 Summary of the Invention [Problem to be solved by the invention]

[0004] The embodiments have been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a light emitting device that can achieve both high heat dissipation properties and suppression of warping. [Means for solving the problem]

[0005] A light emitting device according to an embodiment includes a first substrate, a second substrate disposed on the first substrate, elongated in a first direction in a top view and having a thermal expansion coefficient different from that of the first substrate, a plurality of light emitting elements disposed on the second substrate, and a bonding member bonding the second substrate to the first substrate. The bonding member has a first portion whose length in the first direction is equal to or less than its length in a second direction perpendicular to the first direction, and second portions disposed on both sides of the first portion in the first direction, whose Young's modulus is lower than that of the first portion and whose thermal conductivity is lower than that of the first portion. Effect of the Invention

[0006] According to the embodiment, a light emitting device that can achieve both high heat dissipation and suppression of warping can be realized. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a top view showing the light emitting device according to the first embodiment. [Diagram 2] FIG. 2 is a partially enlarged top view showing region II in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. [Figure 4] FIG. 4 is a top view showing a bonding member of the light emitting device according to the first embodiment. [Diagram 5] FIG. 5 is a top view showing a step of disposing the sintered silver paste and the silver paste on the first substrate in the first embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing the occurrence of warping in a light emitting device according to a comparative example. [Figure 7] FIG. 7 is a schematic cross-sectional view showing the occurrence of warping in the light emitting device according to the first embodiment. [Figure 8] FIG. 8 is a top view showing a bonding member of the light emitting device according to the second embodiment. [Figure 9] FIG. 9 is a top view showing a step of disposing the sintered silver paste and the silver paste on the first substrate in the second embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a light emitting device according to the third embodiment. [Figure 11] FIG. 11 is a top view showing a bonding member of the light emitting device according to the third embodiment. [Figure 12] FIG. 12 is a top view showing a step of disposing a sintered silver paste and a silver paste on a first substrate in the third embodiment. [Figure 13] FIG. 13 is a top view showing a bonding member of a light emitting device according to a first modified example of the third embodiment. [Figure 14] FIG. 14 is a top view showing a bonding member of a light emitting device according to a second modified example of the third embodiment. [Figure 15] FIG. 15 is a top view showing a bonding member of a light emitting device according to a third modified example of the third embodiment. [Figure 16] FIG. 16 is a cross-sectional view showing a light emitting device according to the fourth embodiment. [Figure 17] FIG. 17 is a top view showing a bonding member of the light emitting device according to the fourth embodiment. [Figure 18] FIG. 18 is a top view showing a step of disposing a sintered silver paste and a silver paste on a first substrate in the fourth embodiment. [Figure 19] FIG. 19 is a cross-sectional view showing a light emitting device according to a modified example of the fourth embodiment. [Figure 20] FIG. 20 is a top view showing a step of placing a sintered silver paste and a silver paste on a first substrate in a modified example of the fourth embodiment. [Figure 21] FIG. 21 is a cross-sectional view showing a light emitting device according to the fifth embodiment. [Figure 22] FIG. 22 is a cross-sectional view showing a light emitting device according to the sixth embodiment. [Figure 23A] FIG. 23A is a top view showing a bonding member of the light emitting device according to the sixth embodiment. [Figure 23B] FIG. 23B is a bottom view showing the second substrate of the light emitting device according to the sixth embodiment. [Figure 24]FIG. 24 is a partially enlarged cross-sectional view showing the light emitting device according to the seventh embodiment. [Figure 25A] FIG. 25A is a top view showing the sintered silver paste and the arrangement of the silver paste of a sample according to Comparative Example 1 in a test example. [Figure 25B] FIG. 25B is a top view showing the sintered silver paste and the arrangement of the silver paste of the sample according to Example 1 in the test example. [Figure 25C] FIG. 25C is a top view showing the sintered silver paste and the arrangement of the silver paste of the sample according to Example 2 in the test example. [Figure 25D] FIG. 25D is a top view showing the sintered silver paste and the arrangement of the silver paste of the sample according to Example 3 in the test example. [Figure 26A] FIG. 26A is a top view showing a bonding member of a sample according to Comparative Example 1 in a test example. [Figure 26B] FIG. 26B is a top view showing a bonding member of a sample according to Example 1 in a test example. [Figure 26C] FIG. 26C is a top view showing a bonding member of a sample according to Example 2 in a test example. [Figure 26D] FIG. 26C is a top view showing a bonding member of a sample according to Example 3 in a test example. [Figure 27] FIG. 27 is a graph showing the amount of warping of each sample in the test example, with the sample on the horizontal axis and the amount of warping on the vertical axis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <First embodiment> FIG. 1 is a top view showing a light emitting device according to the present embodiment. FIG. 2 is a partially enlarged top view showing region II in FIG. FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. FIG. 4 is a top view showing a bonding member of the light emitting device according to this embodiment.

[0009] Note that each figure is schematic and has been appropriately emphasized and simplified. Furthermore, the aspect ratio and positional relationship of each component may not strictly match between the figures. The same applies to other figures described below.

[0010] First, the configuration of a light emitting device 1 according to this embodiment will be roughly described. As shown in FIGS. 1 to 4, the light emitting device 1 includes a first substrate 10, a second substrate 20, a plurality of light emitting elements 30, and a bonding member 40. The second substrate 20 is disposed on the first substrate. The thermal expansion coefficient of the second substrate 20 is different from that of the first substrate 10. The plurality of light emitting elements 30 are disposed on the second substrate. The bonding member 40 has one first portion 41 and two second portions 42. The Young's modulus of the second portion 42 is lower than that of the first portion 41. The thermal conductivity of the first portion 41 is higher than that of the second portion 42. In FIG. 4, the first substrate 10 is indicated by a solid line, and the second substrate 20 is indicated by a dashed line.

[0011] Hereinafter, for convenience of explanation, the XYZ Cartesian coordinate system is adopted in this specification. The longitudinal direction of the second substrate 20 is the "first direction X", the direction from the first substrate 10 toward the second substrate 20 is the "third direction Z", and the direction perpendicular to the first direction X and the third direction Z is the "second direction Y". The third direction Z, that is, the direction from the first substrate 10 toward the second substrate 20, is also called "up" and the opposite direction is also called "down", but this expression is also for convenience and has no relation to the direction of gravity. In addition, the view from the third direction Z is called "top view". The top view also includes the case where it is assumed that when the light emitting device 1 is viewed from the third direction Z, something that is actually hidden by other components is seen.

[0012] As shown in FIG. 4, the second substrate 20 has a shape elongated in the first direction X. The length L20x of the second substrate 20 in the first direction X is longer than the length L20y of the second substrate 20 in the second direction Y. That is, L20x>L20y. The second portions 42 of the bonding members 40 are disposed on both sides of the first portion 41 in the first direction X. The length L41x of the first portion 41 of the bonding members 40 in the first direction X is less than or equal to the length L41y of the first portion 41 in the second direction Y. That is, L41x≦L41y.

[0013] Next, the configuration of the light emitting device 1 will be described in detail. The first substrate 10 includes, for example, a metal, such as copper (Cu). The first substrate 10 is, for example, a copper core substrate. More specifically, as shown in FIG. 3, in the first substrate 10, a plurality of wiring layers 11 and a plurality of insulating layers 12 are laminated. Wires made of copper are arranged in the wiring layers 11. Vias made of copper are arranged in the insulating layers 12. For this reason, one of the main components of the first substrate 10 is copper. The thickness of the first substrate 10, i.e., the length in the third direction Z, is, for example, 500 μm.

[0014] The second substrate 20 is, for example, a circuit substrate. The second substrate 20 includes, for example, a semiconductor, for example, silicon (Si). More specifically, the second substrate 20 is a semiconductor integrated circuit substrate, for example, an ASIC (Application Specific Integrated Circuit) substrate. The main component of the second substrate 20 is silicon. Therefore, the thermal expansion coefficient of the second substrate 20 is smaller than that of the first substrate 10. The shape of the second substrate 20 is a rectangular plate with the first direction X as the longitudinal direction, the second direction Y as the lateral direction, and the third direction Z as the thickness direction. A metal layer 21 is provided on the lower surface side of the second substrate 20. The second substrate 20 has a semiconductor portion 22 and a metal layer 21.

[0015] The light emitting elements 30 are, for example, LEDs (Light Emitting Diodes). As shown in Fig. 2 and Fig. 3, in the light emitting device 1, a plurality of light emitting elements 30 are arranged, for example, in a matrix along the XY plane. A resin layer 31 is disposed between the light emitting elements 30. The plurality of light emitting elements 30 and the resin layer 31 constitute an LED array 32.

[0016] 3 and 4, the bonding member 40 is disposed over substantially the entire lower surface of the second substrate 20. Therefore, the shape of the bonding member 40 is a rectangular plate with the first direction X as the longitudinal direction, the second direction Y as the lateral direction, and the third direction Z as the thickness direction. The bonding member 40 is in contact with the upper surface of the first substrate 10 and the lower surface of the metal layer 21 of the second substrate 20.

[0017] The first portion 41 of the joining member 40 includes sintered silver. In sintered silver, a large number of silver particles are sintered together. Therefore, the main component of the first portion 41 is silver (Ag). The second portion 42 of the joining member 40 includes solidified silver paste. In the solidified silver paste, silver particles are disposed in a base material made of resin, for example, silicone. Therefore, the main components of the second portion 42 are resin and silver.

[0018] The light emitting device 1 may further include a phosphor layer 61, a plurality of wires 62, and a resin member 63. The phosphor layer 61 is disposed on the LED array 32. In the phosphor layer 61, a phosphor (not shown) is disposed in a base material made of resin. Note that the phosphor layer 61 is omitted in FIG. 2.

[0019] Wires 62 connect terminals (not shown) of first substrate 10 and terminals (not shown) of second substrate 20. Resin member 63 is disposed on the region surrounding the region on first substrate 10 where second substrate 20 is mounted, and on the outer periphery of second substrate 20, and covers wires 62. When viewed from above, resin member 63 has a frame-like shape.

[0020] Next, a method for manufacturing the light emitting device according to this embodiment will be described. FIG. 5 is a top view showing a step of disposing the sintered silver paste and the silver paste on the first substrate in this embodiment. In Figure 5, the region where the first portion 41 of the joining member 40 is to be formed is shown by a dashed double-dashed line as the "first region 41b," and the region where the second portion 42 is to be formed is shown by a dashed double-dashed line as the "second region 42b."

[0021] First, a first substrate 10 is prepared. A structure in which a plurality of light emitting elements 30 are arranged on a second substrate 20 to form an LED array 32 is prepared.

[0022] 5, the sintered silver paste 41a is disposed in the first region 41b on the first substrate 10. For example, the sintered silver paste 41a is disposed in a line extending in the second direction Y. The sintered silver paste 41a contains silver particles and a solvent as main materials.

[0023] Furthermore, silver paste 42a is disposed in second region 42b on first substrate 10. For example, silver paste 42a is composed of Y-shaped portions facing both sides in first direction X and one line-shaped portion extending in second direction Y. Silver paste 42a contains silver particles, thermosetting resin, and a solvent as main materials.

[0024] Next, the structure including the second substrate 20 and the multiple light-emitting elements 30 is brought into contact with the sintered silver paste 41a and the silver paste 42a and pressed against the first substrate 10. As a result, the sintered silver paste 41a is spread over the first region 41b, and the silver paste 42a is spread over the second region 42b.

[0025] Next, the structure including the first substrate 10, the sintered silver paste 41a, the silver paste 42a, the second substrate 20, and the plurality of light-emitting elements 30 is heated to a temperature of, for example, 200° C. As a result, the solvent in the sintered silver paste 41a volatilizes, and the silver particles are sintered together to form the first portion 41. At this time, the silver particles in the first portion 41 react with the metal layer 21 and are bonded. In addition, the solvent in the silver paste 42a volatilizes and the resin hardens. As a result, the silver paste 42a solidifies to form the second portion 42.

[0026] In this manner, the bonding member 40 is formed, and the second substrate 20 is bonded to the first substrate 10. At this time, the shape of the first portion 41 is a substantially rectangular shape in a top view with a length L41x in the first direction X being equal to or less than a length L41y in the second direction Y. The shapes of the two second portions 42 are also substantially rectangular in a top view.

[0027] 3, wires 62 are bonded to the terminals of the first substrate 10 and the terminals of the second substrate 20. Next, a phosphor layer 61 is placed on the LED array 32. Next, a resin member 63 is formed so as to cover the wires 62. In this manner, the light emitting device 1 is manufactured.

[0028] Next, the effects of this embodiment will be described. FIG. 6 is a schematic cross-sectional view showing the occurrence of warping in a light emitting device according to a comparative example. FIG. 7 is a schematic cross-sectional view showing the occurrence of warping in the light emitting device according to this embodiment.

[0029] 6, in a light emitting device 101 according to the comparative example, a bonding member 140 is disposed between a first substrate 10 and a second substrate 20. The bonding member 140 is entirely made of sintered silver.

[0030] At room temperature, when the sintered silver paste 41a is placed on the first substrate 10 and the second substrate 20 is placed thereon, no warping occurs in the structure 160 including the first substrate 10 and the second substrate 20.

[0031] Next, when the sintered silver paste 41a is heated to, for example, 200° C. in order to sinter it, the first substrate 10, which is mainly composed of copper, has a higher thermal expansion coefficient than the second substrate 20, which is mainly composed of silicon, and therefore the first substrate 10 expands more than the second substrate 20. At this stage, the sintering of the sintered silver paste 41a has not yet been completed, and therefore the Young's modulus is low. Therefore, the expansion of the first substrate 10 is not significantly restrained by the second substrate 20, and no significant warping occurs in the structure 160. After that, the sintering of the sintered silver paste 41a is completed, and the joining member 140 is formed.

[0032] Thereafter, when the structure 160 is cooled to room temperature, the first substrate 10 tends to shrink more than the second substrate 20, but at this stage, the second substrate 20 is firmly bonded to the first substrate 10 by the bonding member 140 made of sintered silver. Therefore, the shrinkage of the first substrate 10 is restrained by the second substrate 20, and an upwardly convex warp occurs in the structure 160. This warp remains in the light emitting device 101 after manufacture. When warp occurs in the light emitting device 101, the optical precision decreases.

[0033] 7, in the light emitting device 1 according to this embodiment, the bonding member 40 includes a first portion 41 and a second portion 42 having a lower Young's modulus than the first portion 41. Therefore, when the structure 60 including the first substrate 10 and the second substrate 20 is cooled to room temperature after the bonding member 40 is formed, the contraction of the first substrate 10 is absorbed to some extent by the second portion 42 of the bonding member 40. As a result, warping of the light emitting device 1 can be suppressed.

[0034] Here, Young's modulus can be calculated by the formula E=σ / ε, where ε is strain (amount of elongation), σ is stress (load), and E is Young's modulus. Specifically, Young's modulus can be calculated by applying a load to first portion 41 and second portion 42 and measuring the amount of elongation of first portion 41 and second portion 42 when the load is applied.

[0035] 4, the length L20x of the second substrate 20 in the first direction X is longer than the length L20y of the second direction Y, and therefore, in the light emitting device 1, warping is more likely to occur along the first direction X than along the second direction Y. In this embodiment, the shape of the first portion 41 that restrains the deformation of the first substrate 10 is such that the length L41x in the first direction X is equal to or shorter than the length L41y in the second direction Y, and therefore the restraint in the first direction X is limited. As a result, warping of the light emitting device 1 can be effectively suppressed.

[0036] Furthermore, in the manufactured light emitting device 1, when the light emitting element 30 is caused to emit light, heat is generated. A part of the heat generated in the light emitting element 30 is discharged to the outside via the second substrate 20, the bonding member 40, and the first substrate 10. Since the thermal conductivity of the first portion 41 of the bonding member 40 is higher than that of the second portion 42, the light emitting device 1 has high heat dissipation. On the other hand, if the entire bonding member 40 is formed from silver paste, the occurrence of warping can be suppressed, but the heat dissipation is reduced.

[0037] According to this embodiment, a first portion 41 having a relatively high thermal conductivity and Young's modulus and a second portion 42 having a relatively low thermal conductivity and Young's modulus are arranged on both sides of the first portion 41 in the first direction X, and the length L41x of the first portion 41 in the first direction X is not greater than the length L41y in the second direction Y, thereby realizing a light emitting device 1 that can achieve both high heat dissipation properties and suppression of warping.

[0038] The light emitting device 1 according to the present embodiment can be used as a light source for, for example, an automobile headlamp. In this case, by individually controlling the multiple light emitting elements 30, the intensity distribution of the light emitted from the headlamp can be arbitrarily controlled, and the irradiation range can be selected. In this case, the luminance and heat generation amount of the light emitting elements 30 may differ from each other depending on the position in the LED array 32.

[0039] For example, when high beam irradiation is performed by the headlamp, a high current is supplied to the group of light-emitting elements 30 arranged at the center of the LED array 32 to achieve high brightness. Since a large amount of heat is generated from the group of light-emitting elements 30, it is preferable that the first portion 41 is arranged directly below the group of light-emitting elements 30.

[0040] In the present embodiment, the first portion 41 is formed of sintered silver, and the second portion 42 is formed of silver paste, but the present invention is not limited thereto. The first portion 41 may be formed of a solder material such as AuSn solder or SAC solder. The second portion 42 may be formed of a resin adhesive containing a filler such as Al paste or graphene paste, or may be formed of a resin adhesive such as epoxy resin, silicone resin, or acrylic resin. The first portion 41 may be formed by plating the second portion 42 with Cu, Au, Ag, or the like after the second portion 42 is formed. It is sufficient that the first portion 41 has a higher thermal conductivity than the second portion 42, and the second portion 42 has a lower Young's modulus than the first portion 41.

[0041] <Second embodiment> FIG. 8 is a top view showing a bonding member of the light emitting device according to this embodiment. FIG. 9 is a top view showing a step of disposing the sintered silver paste and the silver paste on the first substrate in this embodiment.

[0042] As shown in FIG. 8, in the light emitting device 2 according to this embodiment, the boundary 43 between the first part 41 and the second part 42 of the bonding member 40 is a curved line that is convex on both sides of the first part 41 in the first direction X in the top view. Since the first part 41 and the second part 42 are three-dimensional objects, the boundary 43 between them is a two-dimensional surface, for example, a curved surface. However, in the top view as in FIG. 8, the boundary 43 is expressed as an intersection line between the upper surface of the bonding member 40 and the boundary 43 that is a curved surface. That is, in the top view, since the first part 41 and the second part 42 are expressed two-dimensionally, the boundary 43 between them is expressed as a one-dimensional line, for example, a curved line.

[0043] As shown in FIG. 9, in the process of placing sintered silver paste 41a and silver paste 42a on the first substrate 10, the bonding member 40 in this embodiment can be realized, for example, by placing the sintered silver paste 41a in a cross shape in the first region 41b and placing the silver paste 42a in an X shape in the second region 42b.

[0044] According to this embodiment, by forming the shape of the boundary 43 into a curved shape that is convex on both sides in the first direction X of the first portion 41, it is possible to prevent the formation of acute corners in the first portion 41 after sintering. This makes it possible to alleviate the concentration of thermal stress and to prevent damage caused by the thermal stress to the second substrate 20 and the light emitting element 30. Other configurations, manufacturing methods, and effects of this embodiment are similar to those of the first embodiment.

[0045] <Third embodiment> FIG. 10 is a cross-sectional view showing a light emitting device according to this embodiment. FIG. 11 is a top view showing a bonding member of the light emitting device according to this embodiment. FIG. 12 is a top view showing a step of disposing the sintered silver paste and the silver paste on the first substrate in this embodiment.

[0046] 10 and 11, the light emitting device 3 according to this embodiment further includes a partition member 44 disposed between the first portion 41 and the second portion 42 of the joining member 40. The material of the partition member 44 is not particularly limited as long as it is a material having heat resistance sufficient to withstand the manufacturing process of the light emitting device 3, and may be formed of, for example, metal or resin.

[0047] In this embodiment, the partitioning member 44 has a frame-like shape, for example, a substantially elliptical ring shape whose length in the second direction Y is longer than its length in the first direction X. A first portion 41 is disposed inside the partitioning member 44, and two second portions 42 are disposed outside the partitioning member 44, i.e., on both sides in the first direction X. In this embodiment, the partitioning member 44 is disposed inside the second substrate 20 in a top view.

[0048] 12, in the manufacturing method of the light emitting device 3, in the step of arranging the sintered silver paste 41a and the silver paste 42a, a partition member 44 is arranged on the first substrate 10, the sintered silver paste 41a is arranged in a cross shape inside the partition member 44, and the silver paste 42a is arranged in an X shape outside the partition member 44, i.e., on both sides in the first direction X. However, the shape in which the sintered silver paste 41a and the silver paste 42a are arranged is not limited to a cross shape or an X shape, and may be any shape.

[0049] According to this embodiment, by providing the partition member 44, it is possible to more precisely control the positions, shapes, and thicknesses of the first portion 41 and the second portion 42. Other configurations, manufacturing methods, and effects of this embodiment are similar to those of the second embodiment.

[0050] <First Modification of the Third Embodiment> FIG. 13 is a top view showing a joining member of the light emitting device according to this modified example. 13, in the light emitting device 3a according to this modification, the partitioning member 44a is frame-shaped, and a part of the partitioning member 44a protrudes from the second substrate 20 in top view. More specifically, in top view, the partitioning member 44a has a generally elliptical shape whose length in the second direction Y is longer than its length in the first direction X, and both ends of the partitioning member 44a in the second direction Y protrude from the second substrate 20. In addition, both ends of the generally elliptical space surrounded by the partitioning member 44a in the second direction Y also protrude from the second substrate 20 in top view.

[0051] According to this modification, a part of the partition member 44a protrudes from the second substrate 20 in top view, so that when the sintered silver paste 41a is sintered, voids and solvent contained in the sintered silver paste 41a can escape to the outside of the joining member 40. This improves the quality of the sintered silver after sintering. The configuration, manufacturing method, and effects of this modification other than those described above are the same as those of the third embodiment.

[0052] <Second Modification of the Third Embodiment> FIG. 14 is a top view showing a joining member of the light emitting device according to this modified example. 14, in the light emitting device 3b according to this modification, the partitioning member 44b has a frame-like shape and is substantially rectangular in top view. The length of the partitioning member 44b in the second direction Y is longer than the length in the first direction X. The configuration, manufacturing method, and effects of this modification other than those described above are the same as those of the third embodiment. Note that, like the first modification of the third embodiment, a part of the partitioning member 44b may be provided to protrude from the second substrate 20.

[0053] <Third Modification of the Third Embodiment> FIG. 15 is a top view showing a joining member of the light emitting device according to this modified example. 15, in a light emitting device 3c according to this modification, the shape of the partition member 44c is not frame-like in top view, but is two rods whose longitudinal direction is in the second direction Y. The two partition members 44c are arranged spaced apart from each other in the first direction X. The first portion 41 is arranged between the two partition members 44c, and the second portions 42 are arranged on both sides of the two partition members 44c in the first direction X. Other configurations, manufacturing methods, and effects of this modification are similar to those of the third embodiment.

[0054] <Fourth embodiment> FIG. 16 is a cross-sectional view showing a light emitting device according to this embodiment. FIG. 17 is a top view showing a bonding member of the light emitting device according to this embodiment. FIG. 18 is a top view showing a step of disposing the sintered silver paste and the silver paste on the first substrate in this embodiment.

[0055] 16 and 17, in the light emitting device 4 according to this embodiment, the first substrate 10 has a protrusion 14 on the upper surface side. The protrusion 14 is made of, for example, copper. The protrusion 14 is disposed between the first portion 41 and the second portion 42 of the bonding member 40.

[0056] In top view, the shape of the protrusion 14 is a frame, for example, a substantially elliptical ring. The length of the protrusion 14 in the second direction Y is equal to or greater than the length in the first direction X. A first portion 41 is disposed inside the protrusion 14, and two second portions 42 are disposed outside the protrusion 14, i.e., on both sides in the first direction X. In this embodiment, the protrusion 14 is disposed inside the second substrate 20 in top view.

[0057] 18, in the manufacturing method of the light emitting device 4 according to this embodiment, in the step of arranging the sintered silver paste 41a and the unsolidified silver paste 42a, the sintered silver paste 41a is arranged in a cross shape inside the protrusion 14 of the first substrate 10, and the silver paste 42a is arranged in an X shape on both sides of the first direction X outside the protrusion 14. However, the shape when arranging the sintered silver paste 41a and the silver paste 42a is not limited to a cross shape or an X shape, and may be any shape. The configuration, manufacturing method, and effects of this embodiment other than those described above are the same as those of the third embodiment.

[0058] <Modification of the fourth embodiment> FIG. 19 is a cross-sectional view showing a light emitting device according to this modified example. FIG. 20 is a top view showing a step of placing the sintered silver paste and the silver paste on the first substrate in this modified example.

[0059] 19, in the light emitting device 4a according to this modification, the first substrate 10 has a groove 15 on the upper surface side. At least one of, for example, both of a part of the first portion 41 and a part of the second portion 42 of the bonding member 40 are disposed in the groove 15. Therefore, the boundary 43 between the first portion 41 and the second portion 42 overlaps with the groove 15 in a top view.

[0060] 20, in the manufacturing method of the light emitting device 4a according to this modification, the sintered silver paste 41a before sintering is disposed in an area surrounded by the groove 15 on the first substrate 10, and the silver paste 42a is disposed on both sides of the groove 15 in the first direction X. As a result, when the sintered silver paste 41a and the silver paste 42a are pushed and spread by the second substrate 20, they fall into the groove 15, thereby preventing further spread. As a result, the position of the boundary 43 can be overlapped with the groove 15 in a top view.

[0061] In this way, the position of the boundary 43 can be controlled by the groove 15, and the positions and shapes of the first portion 41 and the second portion 42 can be controlled with high precision. Other than the above, the configuration, manufacturing method, and effects of this modified example are similar to those of the fourth embodiment.

[0062] <Fifth embodiment> FIG. 21 is a cross-sectional view showing a light emitting device according to this embodiment. 21, in the light emitting device 5 according to this embodiment, the first substrate 10 has a recess 16 on its upper surface side. Then, in top view, the first portion 41 of the bonding member 40 is located within the recess 16. Meanwhile, in top view, the second portions 42 of the bonding member 40 are located on both sides of the recess 16 in the first direction X.

[0063] Therefore, the thickness of the first portion 41, i.e., the length in the third direction Z, is greater than the thickness of the second portion 42. In one example, the thickness of the first substrate 10 is 500 μm, and the depth of the recess 16 is 50 μm. Furthermore, the thickness of the first portion 41 is not less than 60 μm and not more than 80 μm, and the thickness of the second portion 42 is not less than 10 μm and not more than 30 μm.

[0064] In this embodiment, by disposing the sintered silver paste 41a in the recess 16, the first portion 41 can be formed in the recess 16 and in the area immediately above it. This allows the outer edge of the first portion 41 to be defined by the outer edge of the recess 16, improving the shape precision of the first portion 41.

[0065] Furthermore, the thinner the first portion 41 made of sintered silver, the higher the residual stress, so from the viewpoint of residual stress, it is preferable that it is thicker. On the other hand, the thinner the second portion 42 made of silver paste, the better the heat dissipation, so from the viewpoint of heat dissipation, it is preferable that it is thin. In this embodiment, by making the first portion 41 thicker than the second portion 42, it is possible to improve heat dissipation while suppressing residual stress. Other than the above, the configuration, manufacturing method, and effects of this embodiment are the same as those of the first embodiment.

[0066] Sixth embodiment FIG. 22 is a cross-sectional view showing a light emitting device according to this embodiment. FIG. 23A is a top view showing a bonding member of the light emitting device according to this embodiment. FIG. 23B is a bottom view showing the second substrate of the light emitting device according to this embodiment.

[0067] 22, 23A, and 23B, in the light emitting device 6 according to this embodiment, the metal layer 21 of the second substrate 20 is disposed only in a region facing the first portion 41 of the bonding member 40. As a result, the first portion 41 of the bonding member 40 contacts the metal layer 21 of the second substrate 20, and the second portion 42 of the bonding member 40 contacts the semiconductor portion 22 of the second substrate 20. However, in a top view, the outer edge of the metal layer 21 does not necessarily have to strictly coincide with the boundary 43 between the first portion 41 and the second portion 42.

[0068] The sintered silver forming the first portion 41 reacts with the metal layer 21 and bonds to the second substrate 20. For this reason, it is preferable that the first portion 41 contacts the metal layer 21. On the other hand, the silver paste forming the second portion 42 has a higher bonding strength with silicon than with metal. For this reason, it is preferable that the second portion 42 contacts the semiconductor portion 22. In this embodiment, materials that are compatible with each other are bonded together, so the bonding strength between the first substrate 10 and the second substrate 20 is high. Other configurations, manufacturing methods, and effects of this embodiment are the same as those of the first embodiment.

[0069] Seventh embodiment FIG. 24 is a partially enlarged cross-sectional view showing the light emitting device according to this embodiment. As shown in FIG. 24, in the light emitting device 7 according to this embodiment, the end of the first part 41 of the bonding member 40 rides up on the end of the second part 42. Therefore, in a top view, a part of the first part 41 and a part of the second part 42 overlap. The end of the second part 42 may ride up on the end of the first part 41. In this embodiment, in a top view, the boundary 43 between the first part 41 and the second part 42 is an area having a width. In this case, as described above, in a top view, the intersection line between the upper surface of the bonding member 40 and the boundary 43 is expressed as the boundary 43. In a top view, the boundary 43 defined in this manner may be a curved line that is convex on both sides in the first direction X of the first part 41.

[0070] In this embodiment, a part of the silver contained in the sintered silver of the first portion 41 and a part of the silver contained in the silver paste of the second portion 42 melt and bond near the boundary 43. Due to the effect of silver melting and bonding in this way and the anchor effect between the first portion 41 and the second portion 42, the first portion 41 and the second portion 42 are less likely to peel off. As a result, the bonding strength between the first substrate 10 and the second substrate 20 is improved. Other configurations, manufacturing methods, and effects of this embodiment are similar to those of the first embodiment.

[0071] <Test Example> 25A to 25D are top views showing the sintered silver paste and the arrangement of the silver paste in each sample in this test example. 26A to 26D are top views showing the bonding members of the samples in this test example. FIG. 27 is a graph showing the amount of warping for each sample in this test example, with the horizontal axis representing the sample and the vertical axis representing the amount of warping.

[0072] In this test example, a number of samples were produced in which the second substrate 20 was bonded to the first substrate 10 via a bonding member 40. The arrangement of the first portion 41 and the second portion 42 in the bonding member 40 was varied between the samples. The sintered silver paste 41a was sintered and the silver paste 42a was solidified to form the bonding member 40, and then the amount of warping of each sample at a temperature of 50°C was measured.

[0073] 25A and 26A, in the sample S0 according to Comparative Example 1, the length of the first portion 41 in the first direction X is longer than the length of the first portion 41 in the second direction Y. Note that Comparative Example 1 shown in FIGS. 25A and 26A is a different example from the Comparative Example shown in FIG.

[0074] As shown in FIGS. 25B and 26B, sample S1 of Example 1 corresponds to the light emitting device of the above-described first embodiment, and the length of the first portion 41 in the first direction X is shorter than its length in the second direction Y.

[0075] As shown in Figures 25C and 26C, sample S2 of Example 2 corresponds to the light-emitting device of the above-mentioned second embodiment, in which the length of the first portion 41 in the first direction X is shorter than its length in the second direction Y, and the boundary 43 is a curve that is convex on both sides of the first portion 41 in the first direction X.

[0076] As shown in FIGS. 25D and 26D, sample S3 according to Example 3 corresponds to the light emitting device according to the above-described first embodiment, but the length of the first portion 41 in the first direction X is shorter than that of sample S1.

[0077] 27, the amount of warpage of sample S1 according to Example 1 was less than half that of sample S0 according to Comparative Example 1. The amount of warpage of sample S2 according to Example 2 and sample S3 according to Example 3 was smaller than that of sample S1 according to Example 1.

[0078] The above-described embodiments and modifications are examples of the present invention, and the present invention is not limited to these embodiments and modifications. For example, the present invention also includes the above-described embodiments and modifications in which some components or steps are added, deleted, or changed. In addition, the above-described embodiments and modifications can be implemented in combination with each other.

[0079] The present disclosure includes the following aspects.

[0080] (Appendix 1) A first substrate; a second substrate disposed on the first substrate, elongated in a first direction in a top view, and having a thermal expansion coefficient different from that of the first substrate; A plurality of light emitting elements disposed on the second substrate; a bonding member that bonds the second substrate to the first substrate; Equipped with The joining member is a first portion having a length in the first direction that is equal to or shorter than a length in a second direction perpendicular to the first direction; second portions disposed on both sides of the first portion in the first direction, the second portions having a Young's modulus lower than that of the first portion and a thermal conductivity lower than that of the first portion; A light emitting device having the above structure.

[0081] (Appendix 2) 2. The light emitting device according to claim 1, wherein, in a top view, the boundary between the first portion and the second portion is a curve that is convex on both sides of the first portion in the first direction.

[0082] (Appendix 3) 3. The light emitting device according to claim 1, further comprising a partition member disposed between the first portion and the second portion.

[0083] (Appendix 4) The partition member is frame-shaped, 4. The light emitting device according to claim 3, wherein a portion of the partition member protrudes from the second substrate in a top view.

[0084] (Appendix 5) 3. The light emitting device according to claim 1, wherein a part of the first portion and a part of the second portion overlap each other in a top view.

[0085] (Appendix 6) the first substrate has a protrusion on an upper surface side, 3. The light-emitting device according to claim 1, wherein the protrusion is disposed between the first portion and the second portion.

[0086] (Appendix 7) the first substrate has a groove on an upper surface side; 3. The light emitting device according to claim 1, wherein a boundary between the first portion and the second portion overlaps with the groove in a top view.

[0087] (Appendix 8) the first substrate has a recess on an upper surface side; 3. The light emitting device according to claim 1, wherein, in a top view, the first portion is located within the recess.

[0088] (Appendix 9) The second substrate is A semiconductor portion; a metal layer disposed on a lower surface side of the semiconductor portion; having the first portion is in contact with the metal layer; 9. The light emitting device according to claim 1, wherein the second portion is in contact with the semiconductor portion.

[0089] (Appendix 10) the first substrate comprises a metal; 10. The light emitting device according to claim 1, wherein the second substrate includes a semiconductor.

[0090] (Appendix 11) the first portion comprises sintered silver; 11. The light emitting device according to any one of claims 1 to 10, wherein the second portion includes solidified silver paste. [Industrial Applicability]

[0091] The light emitting device of the present disclosure can be used, for example, as a light source for an automobile headlamp. [Explanation of symbols]

[0092] 1, 2, 3, 3a, 3b, 3c, 4, 4a, 5, 6, 7 Light emitting device 10 First board 11 Wiring layer 12 Insulating layer 14 Convex part 15 groove 16 Recess 20 Second board 21 Metal layer 22 Semiconductor part 30 Light emitting element 31 Resin layer 32 LED Array 40 Joint materials 41 Part 1 41a Sintered silver paste 41b 1st area 42 Part 2 42a Silver paste 42b 2nd area 43 Boundary 44, 44a, 44b, 44c Partition members 60 structure 61 Phosphor layer 62 Wire 63 Resin parts 101 Light emitting device 140 Joint materials 160 Structure L20x: Length of the second substrate 20 in the first direction X L20y: Length of the second substrate 20 in the second direction Y L41x: Length of the first portion 41 in the first direction X L41y: the length of the first portion 41 in the second direction Y S0, S1, S2, S3 Samples X 1st direction Y Second direction Z 3rd direction

Claims

1. A first substrate; a second substrate disposed on the first substrate, elongated in a first direction in a top view, and having a thermal expansion coefficient different from that of the first substrate; A plurality of light emitting elements disposed on the second substrate; a bonding member that bonds the second substrate to the first substrate; Equipped with The joining member is a first portion having a length in the first direction that is equal to or less than a length in a second direction perpendicular to the first direction; second portions disposed on both sides of the first portion in the first direction, the second portions having a Young's modulus lower than that of the first portion and a thermal conductivity lower than that of the first portion; A light emitting device having the above structure.

2. The light emitting device according to claim 1 , wherein, in a top view, a boundary between the first portion and the second portion is a curve that is convex on both sides of the first portion in the first direction.

3. The light emitting device according to claim 1 , further comprising a partition member disposed between the first portion and the second portion.

4. The partition member is frame-shaped, The light emitting device according to claim 3 , wherein a part of the partition member protrudes from the second substrate in a top view.

5. The light emitting device according to claim 1 , wherein a part of the first portion and a part of the second portion overlap each other in a top view.

6. the first substrate has a convex portion on an upper surface side, The light emitting device according to claim 1 , wherein the protrusion is disposed between the first portion and the second portion.

7. the first substrate has a groove on an upper surface side; The light emitting device according to claim 1 , wherein a boundary between the first portion and the second portion overlaps with the groove in a top view.

8. the first substrate has a recess on an upper surface side; The light emitting device according to claim 1 , wherein the first portion is located within the recess in a top view.

9. The second substrate is A semiconductor portion; a metal layer disposed on a lower surface side of the semiconductor portion; having the first portion contacts the metal layer; The light emitting device of claim 1 , wherein the second portion contacts the semiconductor portion.

10. the first substrate comprises a metal; The light emitting device according to any one of claims 1 to 9, wherein the second substrate includes a semiconductor.

11. the first portion comprises sintered silver; The light emitting device of any one of claims 1 to 9, wherein the second portion comprises solidified silver paste.

Images